A package found amid Sunday morning's run in Central Park sent NYPD to scan the park.
New York City Road Runners asked runners and spectators to leave their bags at home.
The NYPD and Port Authority police unions sent relief teams to Boston to help cops there.
Yankees fans declared their solidarity with Boston on Tuesday, one day after deadly bombings there.
Commissioner Ray Kelly said New York remained the No. 1 target as 77 suspicious packages were reported.
The bombings killed three people, including an 8-year-old, and reportedly injured more than 170 people.
The hunt for the Boston Marathon bomber is being treated as a potential terrorism probe, the FBI says.
Michael and Victoria Arnstein were close to the finish line when the bombs went off Monday.
Google and the Boston Police Department have set up ways people can find loved ones in Boston.
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